


Troubleding Sons

by Sprinkles257



Series: Dadster and Skelebros stories [1]
Category: Undertale (Video Game)
Genre: Dadster!!, Don't worry the next Dadster work I do will be fluffy, Gaster did NOT create them in the labs (but that's cool too), Gen, Good W. D. Gaster, I'll explain how it works later...I have weird headcanons lol, Should I add a bullying warning?, The title is a play on words hehe, This AU is so angsty and GOOD, bad brother au, but if it is please let me know, i don't think it's that bad
Language: English
Status: Completed
Published: 2018-01-17
Updated: 2018-01-17
Packaged: 2019-03-02 21:26:51
Rating: Teen And Up Audiences
Warnings: Major Character Death
Chapters: 3
Words: 3,374
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/13326690
Author URL: https://archiveofourown.org/users/Sprinkles257/pseuds/Sprinkles257
Summary: "W.D. Gaster loved his sons, but he wished they loved each other. Well, they tried to, but it just didn’t work out. His first son, Sans, seemed to be a little bitter towards his second son, Papyrus. Gaster supposed that was a feeling a lot of older siblings had."





	1. Right?

**Author's Note:**

> I wish there was more stuff on the Bad Brother AU out there. The skelebros' relationship is so good and adorable...but do you know what's cool too? The complete opposite! I love some angst sometimes. I might add some fluff in this as well, but...who knows? :P  
> Thank you for reading in advance!  
> (The creator of the AU is here: http://ask-the-great-papyrus.tumblr.com/)

 

   W.D. Gaster loved his sons, but he wished they loved each other. Well, they _tried_ to, but it just didn’t work out. His first son, Sans, seemed to be a little bitter towards his second son, Papyrus. Gaster supposed that was a feeling a lot of older siblings had.

   Sans was actually a nice kid. He liked jokes (especially knock-knock jokes and sometimes puns), and was showing to be adept with math. Of course, at this age, he wasn’t a genius, but Gaster hoped he would do well in the future.

   Papyrus, well…he was sweet. A little loud, and picky, but he cared for others just as much as he did himself. Unfortunately, he never really got the hang of making friends. It wasn’t that he didn’t understand how to, that was actually what he was best at – understanding others’ feelings. He just couldn’t take those thoughts and convert them into ways of socializing very well. Due to these facts, the little skeleton had bouts of loneliness here and there.

   (In other timelines, Sans, and Gaster if he was present, would support him. In this timeline…not so much.)

   When Sans first discovered he had a little brother, he was four years old. He was rather angry that day. Gaster tried to assure his son that he _wasn’t_ being replaced. He honestly just liked the idea of having two kids – it would pay off for all of them in the end, he thought. W.D. Gaster was the Royal Scientist, and he knew the measures he was taking to destroy the barrier were risky. When he was…no longer around, he wanted his sons to have someone to depend on, to care for – each other.

* * *

 

   When Papyrus first learned to speak, he…well, he took advantage of his ability. Yes, it was rather repetitive, but that was just the little skeleton’s way of learning. Gaster wasn’t bothered – if he was, he didn’t show it. He was a calm type of monster, but he could take responsibility too if need be. Sans didn’t really bother to hide it.

   One day, Papyrus came up to his brother and said, “SANS!” to get his attention. His brother’s name was his first word, by the way. Gaster found it very bittersweet. He also found it a bit odd that a child’s vocabulary was influenced by the people closest to them, and Papyrus’s first word was the name of the monster that _ignored him._

   (Although, Gaster would later find out that his second son developed his proper way of speaking. Papyrus could be casual too, however.)

   Sans didn’t really know what to expect. Of _course_ his annoying little brother chose him to learn by. Not only that, but he didn’t think he was a very good example, either!

* * *

 

   On Gyftmas a few years later (Sans was 10 and Papyrus was 6), the skeleton family was giving each other presents.

   [HERE YOU GO, SONS. I HOPE YOU ENJOY THEM.] Gaster said with a smile. He gave Papyrus a ‘color cube’ (he noticed he took a liking to puzzles), who examined the object and then started to mess with it. He gave Sans a science fiction book, “From the Earth to the Moon” by Jules Verne. It was an old human book that the eldest skeleton found at the dump (he was looking for parts for his project, and found that by chance).

   “thanks, dad.” Sans said, grinning.

   A few moments later, the youngest skeleton excitedly lifted his puzzle. He solved it remarkably quickly.

   “DADDY, SANS! I DID IT!”

   [HEH. INDEED, PAPYRUS.] Gaster put his hand on his son’s head as an affirming gesture.

   Sans gazed at the cube. There were one or two off-colored squares, but otherwise it was almost perfectly solved. "wait. didn't you just get this a minute ago?"

   "YEP!"

   “...hm. good job, i guess.” The skeleton child looked back to his father. “by the way, i made a card for you. papyrus, uh…he ‘helped’.”

   The card read:

_merry gyftmas. hope it goes well for you, because you make days go well for me. thanks._

_-sans_

Under the writing was an inverted blue heart with “PAPYRUS” next to it. The ‘y’ was backwards.

   [OH, THANK YOU. IT IS VERY NICE.]

   Papyrus then gave his brother a card, who nodded. He apologized for not giving one back, because he forgot. The little skeleton’s eyebrows creased, but he knew he shouldn’t get angry – even at forgetting something simple such as a card. He’s not mad. It was just a mistake…

   Right?

   “IT’S OKAY!"

"...THANKS ANYWAY."


	2. Enter Adolescence!

**Summary for the Chapter:**

> "As the skeleton brothers become teens, things begin to get a little more...  
> Complicated."

**Notes for the Chapter:**

> And by complicated, I mean worse. Hehe.  
> (I know I'm evil. >:D)  
> \---  
> Gaster headcanons:  
> \- I like to think the holes in his hands are just a physical deformity. Nothing angsty about skeleton hands here. XD  
> -Also, another headcanon about him: he's cool and collected, but can also be a dork sometimes. He makes dry-humored jokes.  
> \- His eye lights are visible ONLY when he's feeling a strong emotion (like how Sans's eye lights disappear when he's serious)  
> \---  
> Writing dialogue between Gaster and Papyrus is fun because it's just a bunch of ALL CAPS.  
> Thank you, and enjoy!

   Years later, the skeleton brothers began adolescence. Papyrus was 13, and Sans was 17. Sans was now old enough to get a job, so he decided to assist his father in the Lab. At this time, they lived at the edge of Snowdin, entering Waterfall. It was the closest to the Hotland labs as they could get. Papyrus, of course, was still in school. Both of the skeletons used to be homeschooled (what better teacher than your father that's also a scientist?), but now that Sans also had a job, his brother had to go to public school.

   Papyrus liked it there! Some monsters were really nice. Some...were not - but he tried not to let them get to him. His grades were good. He usually got B's. Sure, that wasn't the best, but it's still above average and he was trying! However, on the downside - once he got back to the house, he was all by himself. Sometimes he had to admit, great as he was, he wished his dad and brother would be here more often. W.D. Gaster used to be at the house more, but now that his project is progressing he must be at the Lab often. Sans, though...When he wasn't at school he was at work now. Come to think of it, he never really played with his brother much at all, did he?

   The teenage skeleton contemplated on that for a while. When they were younger, Sans was neither nice nor mean to him. He just kind of stayed away, aside from the occasional "hm, that's nice." or joke. Papyrus liked his share of jokes and japes, but the ones from his brother were a little weird, he had to say. However, things were gradually changing, which is to be expected with time. Many things  _did_ change already. For instance - the Lab, and also, Papyrus surpassed both of his relatives' heights. Gaster was average in height, and Sans was a little on the shorter side. Papyrus was only  _slightly_ taller than his father, but he considered it a win nonetheless.

   Slowly, their personalities were changing too. As the skeleton brothers became teens, things began to get a little more...Complicated.

   Was there a reason why Sans didn't want to spend time with him? Maybe those mean monsters were right about him - was he too weird? Too loud? 

   Maybe he wasn't as great as he thought.

**~Meanwhile, at the lab...~**

   W.D. Gaster was having a breakthrough. His plan on the CORE was going wonderfully - he just needed to work out the errors. Right now, King Asgore was visiting to discuss the plan. Gaster wasn't very familiar with the king, but below the grief, he thought of him as a pleasant monster. 

   [HELLO, YOUR MAJESTY.] 

   "Howdy, Doctor Gaster." It was very hard for a monster that wasn't a skeleton to understand the symbol-based fonts - such as Wingdings. However, so as to understand his Royal Scientist, Asgore learned it. 

   [THE CORE IS FUNCTIONING VERY WELL. HOWEVER, THERE ARE A FEW THINGS TO FIX. I SUGGEST WE ONLY ALLOW AUTHORIZED MONSTERS IN UNTIL THEN.]

   "Of course. Thank you. I really appreciate you helping us."

   [US? HEH, IS SOMEONE WITH YOU?]  Asgore had to chuckle a bit. Gaster was usually calm, but when around those he was comfortable with, he could be playful too.

   "Ohoho! I meant the kingdom."

   [INDEED. THANK  _YOU_ FOR LEADING US.]

   Asgore gave a tired smile. Leading is a very large responsibility, especially for someone who has had lost some things. The king was grateful for all the help he received over the years.

   The two conversed more over general things, and then Gaster went into more detail with the CORE.

   [AHEM. WELL, I SUPPOSE NOW WOULD BE A GOOD TIME TO END THIS. I ENJOYED THIS TALK, KING ASGORE.] The skeleton monster held out his hand, and Asgore shook it. His grasp was strong, but warm.

  "So did I, Doctor Gaster. I'll be on my way." 

   The went their own ways. Gaster should get back to Sans now. And Papyrus...Oh, Papyrus. The elder skeleton felt rather guilty for leaving his son alone. Maybe he should have a talk with him later. So many things to do and not enough time.

-

    "dad."

  [WHAT IF HE GETS HURT?]

   "dad."

   [WHAT DOES HE THINK OF US?]

   " _dad._ "

   [YES, SANS.]

   "it's not like you to get worked up over something this small. i'm sure papyrus is fine."

   [WHILE I APPRECIATE THE REASSURANCE, I DON'T THINK YOUR BROTHER IS 'SOMETHING SMALL.']

    Sans didn't protest. Papyrus wasn't 'something small', but he wasn't exactly the picture of brilliance either. In Sans's eyes, he was just...there. He didn't  _hate_ his brother, per say, but he didn't like him. He was just annoying, just _there_. 

   "mm. if you're worried about him, why don't you just go home for tonight? i'll clean up shop for you."

   [...YOU'RE GOING TO PUT 'BONEHEAD' SIGNS ON THE BACKS OF CO-WORKERS, AREN'T YOU.]

   "heh, you know me too well."

   [...OH, ALRIGHT. JUST THIS ONCE, YOUNG MAN.]

**~Back at the house...~**

   Gaster opened the door, hoping to find his son in the house. [PAPYRUS? I'M HOME!]

   "F-FATHER?!" Gaster heard a crash and saw a teenage skeleton racing down the stairway. "YOU'RE HERE."

   [I AM. ARE YOU ALRIGHT?]

   "I...YEAH. I WAS JUST SURPRISED." Papyrus was  _surprised_ to see him? Yikes.

   [SON, IF NOW IS APPROPRIATE, I WOULD LIKE TO DISCUSS SOME THINGS WITH YOU.]

   Oh no. Was that a good thing or a bad thing? Papyrus could only hope for the best. "OF COURSE!"

-

   The elder skeleton and his son sat down in the living room. Gaster looked neutral. Papyrus looked...pensive.

   [ANSWER THIS QUESTION HONESTLY, ALRIGHT?]

   "OKAY."

   [DO YOU FEEL LEFT OUT?]

   "...COULD I GET A DIFFERENT QUESTION?"

   [I'M AFRAID THAT'S THE ONLY ONE.]

   Papyrus looked his dad in the eye sockets. He just didn't want to say it. Sans was a 17 year old -  _almost adult_ \- apprentice, and he was just in school by himself. What would Gaster think of his son?

   "FATHER. AM I A PROBLEM?"

   Gaster's eye lights appeared. [WH- NO. STARS, NO. WHAT MADE YOU THINK SO?]

   Papyrus could have said many things. He could have said that that yes, he  _did_ feel left out. He felt like a burden sometimes. He just usually tried not to show it - what's the point in feeling sad when you can get better, right?

   That strategy wasn't working out very well right now.

   "WELL, I...TO ANSWER YOUR QUESTION, I DO FEEL A BIT LEFT OUT. I FEEL THAT I'M NOT DOING ENOUGH."

   Gaster, in spite of himself, had to chuckle just a bit. [AT 13 YEARS OLD, YOU ARE DOING ENOUGH.] He put his hands on his son's shoulders - it was a habit he seemed to gain over the years. [YOU ARE VERY SMART, SON. JUST NOT IN A WAY THAT CAN BE MEASURED BY NUMBERS OR EQUATIONS.]

   "...WHAT ABOUT SANS?"

   [FROM WHAT I CAN SEE, SANS IS DOING VERY WELL IN THE LAB.]

   "THAT'S GOOD. I HAVE SOMETHING TO ASK, THOUGH."

   [YES?]

   Oh, how to word such a thing... "DO YOU KNOW WHY HE, UM, KEEPS HIS DISTANCE FROM ME?" Yes, the elder skeleton knew why Sans avoided his brother. It seemed he wasn't too in favor of him. On the good hand though, Sans has never been needlessly rude. Gaster considered interfering, and he internally felt guilty for not doing so. He thought maybe, just  _ma_ _ybe,_ his sons would work it out as they got older. Problem solving was a necessity, wasn't it? 

   He just wanted to have a nice family, but it was too late now.

   [PAPYRUS...I KNOW OUR FAMILY IS DIFFERENT FROM SOME OTHERS YOU SEE, BUT I ASSURE YOU, YOUR BROTHER DOES NOT HATE YOU. I  _DEFINITELY_ DON'T HATE YOU. YOU ARE NOT A PROBLEM, END OF DISCUSSION.]

   The teenage skeleton's eye sockets glistened. He wasn't sure if it was from tears or happiness at hearing his dad say that. The happiness was rather short lived ( _IT SHOULDN'T BE,_ he thought), but it counted. However, there was still a question that needed to be answered.

   "THANK YOU, FATHER. THAT MEANS A LOT TO ME."

It meant more than both of them had expected.


	3. The Accidental Adulthood

**Summary for the Chapter:**

> The Accident.  
> Also, after this it's pretty much a huge time jump to the days right before Frisk is supposed to arrive. XD

**Notes for the Chapter:**

> Here we go, the (I think) last chapter! I hope this was worth reading. :)  
> I know the CORE accident has been done a bajillion times, and I love all versions of it, but I tried to do mine.  
> (Sorry, I might say that frequently.)  
> I have never written an action scene, so, uh...I hoped for the best!  
> "Sugar and Ice" - http://tvtropes.org/pmwiki/pmwiki.php/Main/SugarAndIcePersonality

   The Hotland Lab was chaotic.

   Scientists, assistants and the like were all running, flying, or rapidly moving in the way they do. In the midst of it all, was Sans. He knew that the CORE had some errors that needed to be fixed, but  _this_ was more than a minor mistake. He overheard others' voices, murmuring and shouting, blending together into garbled nonsense. The Lab's warning alarm flashed. It really was a mess, and that was something coming from a monster who was known for  _mess_ ing around.

   ...Okay, now was not the time for that. He had to find Gaster. Others (if he heard correctly) were wondering the same thing.

   "Where is Dr. Gaster?!"

   "Calm down, he's the Royal Scientist. He must know what he's doing, r-right?"

   "THAT IS NOT THE ISSUE RIGHT NOW! We need to find a way to stop this."

   "Oh god, oh god, oh god-"

   Sans tried to move swiftly through the scene. Usually working beside his father, he had a little more information about the project than the other assistants. He had to find a control panel of some kind. He almost found one until he heard an odd-sounding shriek.

   [SAAAAAAANNS!] Oh, no. There was only one monster that sounded like that.

    _keep your priorities...your priorities._ Oh, who was he kidding? He wasn't just going to let his father dust. He should probably go.

   -

   He followed the sound of Gaster's voice, to find...the ledge. The ledge that the Royal Scientist himself requested only those with permission can enter - because it was  _dangerous._

   "holy  _shit._ dad, are you down there?"

   [YES!]

   "i...i have to get you out of this thing."

   [NO, DON'T! IT...IT'S FOR THE BEST. I HAVE TO COMPLETE THE- THE PLAN, BUT I DON'T THINK THAT'S POSSIBLE. THE ONLY THINGS MORE IMPORTANT THAN THE BARRIER ARE THE MONSTERS IN IT. THESE WORKERS-NGH-  _YOU_ DESERVE TO LIVE.]

   Sans had never seen his father in a more desperate state. Those who didn't know Gaster usually thought of him as the "cold and calculating" type. No. He was  _so much more_ than that. Calm and cold were two different things. Here he was, on the day on like likely death, talking not of himself but of the  _community._ He was practically sacrificing himself. Did he want to die? Of course not! Although, now that he was in such a horrible situation, he decided to just expect the worst and hope for the best.

   Gaster thought back to that time a few months ago when Papyrus said he was left out. Well, the CORE  _did_ power the Underground, but its power was mainly intended to help break the barrier. It was either the "power method", as he nicknamed it. It would mimic the power of a human soul to  _time travel._ He knew how dangerous time could be when tampered with.

    Maybe now he would understand how Papyrus felt.

   "i'm not just gonna let you dust yourself." Sans stated, bringing the elder skeleton out of his not-so-pleasant thoughts.

   [SANS, PLEASE. I'M RUNNING OUT OF TIME. JUST LET ME SPEAK.]

   "uh, okay?"

   [I WILL ALWAYS- GHHK! - REMEMBER YOU, AND YOUR BROTHER. PLEASE TAKE CARE OF HIM FOR ME. ONE LAST THING.]

   [DON'T, F-AH-ORGET MEEEEeee..........]

   "forget wha-"

   There was a blinding flash of white.

   And then he was gone. 

-

   Nobody remembered W.D. Gaster. Except for those close in proximity to the accident, and those were still only very faint memories.

   Sans walked into the house he and...his brother lived in. "papyrus!" he called.

   Papyrus ran to the door and looked up. He heard there was a problem with the CORE from the news, but didn't know the details. "YOU'RE HOME EARLY."

   "mm, surprising. who owns this house?"

   The teenage skeleton stared for a moment, before grinning. "THAT'S AN ODD QUESTION. YOU, SILLY!"

   "...me, huh." He owned the house? Well, he  _was_ 18 now. He supposed, being the only adult in the household, it made sense. Also, was Papyrus always this cheerful? He doesn't remember spending time with him, so he can't tell if he was. He had to admit, being around his brother made Sans feel...weird. There was some type of resentment within him without a cause. The incessant, "tip-of-the-tongue" feeling was just making it worse. "i gotta go."

   "ALRIGHT. BYE!"

-

   Over the passing years, Sans still couldn't shake these feelings. He ended up doing things that his past self, even with the bitterness, would have regretted. He found out about a casual restaurant named Grillby's, which he frequented. His personality became much more laid-back. However, with his brother, it seemed to be more of a "sugar and ice" type of personality. He seemed to take his anger (?) out on Papyrus, and be slightly warmer to others. The young skeleton started out cheerful, and slowly diminished. He was still very energetic, it just didn't have the same mirth as it did at one time. He still made jokes, but they were either mocking towards Papyrus or self-deprecating. He also heard there was a new Royal Scientist - Dr. Alphys. He's met her a few times while he worked in the...Lab? Yeah, that.

   On a particularly bad day, Sans let himself slip. He was suddenly hit by a chunk of memory. It was a man...a skeleton, like him. However, he was deformed. There were deep cracks on his eye sockets - one above, one below. He was not solid, but not liquid either. He was dead, but alive.

   He was nowhere, but everywhere.

   The man kept calling his name.

   [SANS!]

   [SANS, CAN YOU HEAR ME?]

   [WHY DID I DO THIS?]

   [...I'M SORRY.]

   "SANS, PLEASE!"

   "aaaaghh!" The small skeleton looked up to see his brother's face - worried face, at that. "what...what are you doing?"

   "YOU LOOKED DEEP IN THOUGHT, AND THEN YOU JUST FELL UNCONSCIOUS WITHOUT WARNING!"

   "since when does falling unconscious  _ever_ have a warning?"

   Papyrus sighed. He just wanted to help. "WHAT I MEAN IS, I WAS WORRIED, SO I BROUGHT YOU INSIDE. THE OTHER SNOWDIN CITIZENS WERE STARING. SORRY FOR THAT."

   "it's...it's fine. just leave me alone, ok?"

   For a moment, anger flashed across the tall skeleton's face. "I WASN'T GOING TO LEAVE YOU TO DUST."

   Sans's eye sockets widened. Has...has he heard that before? (He doesn't know it, but yes, he has.  _He_ said it.) "ghh- fine. you can stay. don't see why you'd want to, though..."

   "I  _DO_ WANT TO, BECAUSE YOU MATTER TO ME." Papyrus knew Sans wasn't the nicest towards him, that was obvious. However, he cared about him, and he knew the small skeleton did too, somewhere.

   "why...why are you nice to me after all the crap i say to you? you don't have a reason to."

   "BEING KIND NEVER NEEDS A REASON." Although tentatively, the tall skeleton held out his hand to his brother. "EVERYONE DESERVES A SECOND CHANCE."

   It was at that moment that Sans realized if he did one thing differently, his whole life would have been different. Maybe this 'annoying little brother' of his would turn out to be great, and maybe he would be better too. They could have supported each other not just now, but _all the time_. Things were bad now, but maybe they would get better. With hope.

   Slowly, he placed his hand on his brother's palm. He murmured words he never thought he'd say.

"...thanks, bro."

   


End file.
